Tornado Thread: HIGH RISK in Oklahoma and Kansas

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Cape values today are ridiculous,

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SUMMARY...Thunderstorms are expected to increase in coverage early
this afternoon across the southern Plains. Very large hail,
tornadoes, and damaging wind gusts will be possible. A tornado watch
will be needed within the next hour or so.

DISCUSSION...Visible satellite imagery depicts a developing cumulus
field across parts of Texas Rolling Plains this afternoon. With
ongoing surface heating and continued moistening of low levels,
convective inhibition has diminished considerably, as suggested by
surface observations, mesoanalysis, and forecast sounding data.
While not directly sampling the plume of greatest 850mb moisture
farther west, the 15Z OUN sounding sampled a deepening/moistening
boundary layer (as compared to the 12Z sounding). In turn, as broad
ascent associated with the western U.S. trough overspreads the
region, initiation of deep moist convection is expected early this
afternoon, with storms likely forming across the Texas Rolling
Plains along/east of the dry line. Indeed, two separate areas of
initiation are possible -- one within the broad warm sector near
subtle confluence/differential heating boundaries and another closer
to the dry line.

Regional 12Z soundings sampled very steep mid-level lapse rates (8-9
C/km) atop rich boundary-layer moisture spreading northward.
Continued heating of the boundary layer has promoted moderate/strong
buoyancy across the warm sector, with MLCAPE values upwards of
3000-4000 J/kg. In combination with sufficient effective shear
upwards of 40-45 kt, this thermodynamic environment will favor
strong/rotating mid-level updrafts, quite favorable for very large
hail in discrete cells and embedded cores. Additionally, some
veering with height of low-level winds and ample boundary-layer
moisture will encourage a tornadic threat, especially with
supercells that acquire a more eastward propagation component.
Damaging winds will also be a considerable threat, as dry mid-level
air favors ample evaporative cooling and strong downward momentum in
precipitation cores. Any upscale growth/cell mergers will further
enhance this threat. A tornado watch is expected within the next
hour or so.

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SUMMARY...Severe thunderstorms will develop across portions of
western Oklahoma this afternoon. Tornadoes, a few of which may be
strong, very large hail, and damaging winds will be possible. A PDS
(Particularly Dangerous Situation) tornado watch will be issued
within the next hour.

DISCUSSION...As mid-level forcing for ascent gradually increases
this afternoon, thunderstorms will increase in coverage across much
of the region over the next 1-3 hours. Surface observations indicate
dew points have risen into the mid/upper 60s over much of the
discussion area. Wave/billow structures on visible satellite suggest
convective inhibition remains over parts of Oklahoma and Kansas this
afternoon, but continued boundary-layer heating/moistening and
cooling aloft are forecast to remove any remaining inhibition. In
turn, as the dry line focuses near the Oklahoma/Texas border,
thunderstorms will develop and likely become severe quite quickly.
Moreover, open warm sector development is also possible across
portions of southwest Oklahoma, within zones of confluence and
differential heating.

With the presence of moderate/strong buoyancy (around 2500-3500 J/kg
of MLCAPE) and effective shear upwards of 45-50 kt, initial
supercellular modes appear probable. Some forecast soundings
indicate a deep-layer wind profile marginally supportive of a few
left splits with initial warm sector development east of the dry
line this afternoon. Cell mergers/interference would preclude a
higher-end severe threat. However, as low-level hodographs enlargen
(with greater clockwise looping) late this afternoon into this
evening, cyclonically rotating supercells may become favored, with a
greater eastward component of movement. Any such discrete cell would
possess a threat for tornadoes (which could be strong), very large
hail, and damaging winds.

Farther west along the dry line, severe thunderstorms will likely
organize near the Oklahoma/Texas Panhandle border. Some potential
exists for northward-moving cells (from initial convection to the
south) to interfere with these cells, as well as cause convective
overturning, which would limit the severe threat some. However, the
genesis region of the southern cells, as well as their expected
motion, will likely keep them east of cells generating along the dry
line. In turn, a relatively pristine air mass should exist for
supercellular development by mid/late afternoon. Backed surface flow
and increasing boundary-layer moisture ahead of the dry line will
favor a threat of tornadoes, a few of which could be strong. Very
large hail and damaging winds will also be possible. A PDS
(Particularly Dangerous Situation) tornado watch will be issued
within the next hour.

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